Heat the oven to 275°F (135°C). Combine the brown sugar, paprika, garlic powder, onion powder, salt, and pepper.
Rub the ribs all over with the spice mixture. Place them on a foil-lined sheet pan, add the water and vinegar, cover tightly, and bake for 2 1/2 hours.
Glaze:
Warm the barbecue sauce in a saucepan. Remove the foil and brush the ribs generously with sauce.
Increase the oven to 425°F (220°C) and bake uncovered for 15 to 20 minutes, brushing once more, until glossy and caramelized.
Serve:
Rest the ribs for 10 minutes, slice between the bones, and serve with coleslaw, cornbread, and pickles.
Notes
For extra char, finish the sauced ribs under the broiler for 1 to 2 minutes.
Let the ribs rest before slicing to keep the meat juicy.